Method of and apparatus for measuring pressure, especially vacuum pressure
A pressure step (ps) is applied to the interior of a compartment (1). By means of a sensor (5) which monitors the pressure within compartment (1), besides of the prevailing pressure level (pST), the transient step response oscillation frequency (fTSR) is registered as indicative of the gas or gas mixture present in the compartment (1).
The present invention is directed on a method of measuring a pressure, thereby especially vacuum pressure, of a gas or gas mixture in a compartment.
It is an object of the present invention to improve such method and apparatus.
This is achieved by the method of measuring pressure, especially vacuum pressure, of a gas or a gas mixture in a compartment of predetermined geometry of inner space, which comprises measuring the pressure by a pressure sensor. At least one step of pressure is applied to the compartment, and the transient step response oscillation frequency—fTSR—is monitored by the addressed pressure sensor in the compartment. The result of monitoring is considered as indicative of the gas or gas mixture in the compartment. The measuring of the addressed pressure by the pressure sensor lasts longer than the transient step response, which means that the more or less stationary pressure level in the compartment before and/or after applying the pressure step, is measured as e.g. for controlling a process which is performed in the compartment at a desired pressure level.
In an embodiment of the method according to the invention, which may be combined with any embodiment thereof still to be addressed, unless in contradiction, applying of the at least one step of pressure comprises applying a pressure step from ambient pressure to a target pressure, preferably to a target vacuum pressure.
In a further embodiment of the method, which may be combined with any of the preaddressed embodiments and with any embodiment still to be addressed, unless in contradiction, applying the at least one step of pressure comprises applying a pressure step from a pressure in the compartment, preferably a vacuum pressure, to ambient pressure.
In an embodiment of the method, which may be combined with any of the preaddressed embodiments as well as with any embodiment still to be addressed, unless in contradiction, applying the at least one pressure step is performed by abruptly expanding a gas from the compartment or into the compartment.
In a further embodiment of the method according to the invention, which may be combined with any of the preaddressed embodiments and with any of the embodiments still to be addressed, unless in contradiction, monitoring the fTSR is performed in time domain or in frequency domain.
In a further embodiment of the method, which may be combined with any of the embodiments of the method already addressed as well as with any embodiment still to be addressed, unless in contradiction, at least one reference fTSR signal indicative for a fTSR of at least one gas or gas mixture is provided.
A signal which depends from the fTSR as monitored is compared with the addressed at least one reference fTSR signal.
In an embodiment of the just addressed embodiment there is provided a multitude of gas or gas mixture specific reference fTSR signals, preferably in form of a look-up table. The signal dependent from the fTSR as monitored by the pressure sensor is compared with the reference fTSR signals. Thereby, a signal is output which is indicative for a gas or gas mixture, the reference fTSR signal thereof fitting best with the signal dependent from the fTSR as monitored.
In an embodiment of the method according to the invention, which may be combined with any of the preaddressed embodiments and embodiments still to be addressed, unless in contradiction, the at least one reference fTSR signal is provided by providing a reference compartment of predetermined geometry of inner space and applying to the reference compartment at least one reference step of pressure, monitoring by a further pressure sensor the resulting fTSR and storing a signal dependent from the addressed resulting fTSR occurring in the reference compartment, as reference fTSR signal.
In an embodiment of the just addressed embodiment the dependent signal stored is derived from the resulting fTSR as a function of at least one of:
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- a difference of predetermined geometries of the compartment and of the reference compartment, if at all existing and if relevant and not neglectable;
- a difference of pressure levels at which the fTSR in the reference compartment and in the compartment are monitored, if at all existing and if relevant and not neglectable;
- a difference of temperatures, at which the fTSR are monitored in the reference compartment and in the compartment, if at all existing and if relevant and not neglectable.
A further embodiment, which may be combined with any of the embodiments already addressed and still to be addressed, unless in contradiction, comprises deriving the signal dependent from the fTSR as monitored as a function of at least one of
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- a difference of predetermined geometries of the compartment and of the reference compartment, if at all existing and if relevant and not neglectable;
- a difference of pressure levels at which the fTSR in the reference compartment and in the compartment are monitored, if at all existing and if relevant and not neglect able;
- a difference of temperatures, at which the fTSR in the reference compartment and in the compartment are monitored, if at all existing and if relevant and not neglectable.
In one embodiment of the method according to the invention, which may be combined with any of the preaddressed embodiments and embodiments still to be addressed, unless in contradiction, the geometry of the reference compartment is equal to the geometry of the compartment or the reference compartment is realized by the compartment.
In a further embodiment of the method, which may be combined with any of the preaddressed embodiments and any embodiment still to be addressed, unless in contradiction, the further pressure sensor is selected to be equal to the pressure sensor for measuring and monitoring or the further pressure sensor is realized by the addressed pressure sensor.
In a further embodiment of the method which may be combined with any of the preaddressed embodiments and embodiments still to be addressed, unless in contradiction, there is valid at least one of:
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- The step of reference pressure is equal to the step of pressure as applied to the compartment to be monitored and measured,
- The pressure level in the reference compartment before the reference step is applied is equal to the pressure level in the compartment before, the step is applied there.
- The stationary pressure level in the reference compartment after the reference step is applied is equal to the stationary pressure level in the compartment after the pressure step is applied there.
- The temperature in the reference compartment during applying the reference step is equal to the temperature in the compartment during the pressure step being applied there.
In a further embodiment of the method, which may be combined with any of the preaddressed embodiments and embodiments still to be addressed, unless in contradiction, at least monitoring by the sensor comprises sampling a signal dependent from an output signal of the sensor at a sampling frequency which is at least 5 times, preferably at least 10 times higher than the fTSR, the sampling frequency being at least 0.5 kHz, and even more preferred at least 5 kHz.
Besides of monitoring also the addressed measuring may, and normally is performed by the addressed sampling.
In a further embodiment of the method according to the invention, which may be combined with any of the preaddressed embodiments and any embodiment still to be addressed, unless in contradiction, measuring and monitoring by the pressure sensor comprises
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- Providing a pressure sensing capacitor with two electrodes, the capacity of the capacitor being dependent from pressure in the compartment and
- electrically monitoring the course of the capacity of the addressed capacitor.
In an embodiment of the just addressed embodiment the course of the addressed capacity is monitored by sampling, whereby each sampling step comprises charging and discharging the capacitor, thereby performing at least one of charging and of discharging of the capacitor via a resistive element of predetermined resistivity. The addressed resistive element is thereby, together with the addressed capacity, decisive for the time course of the at least one of charging and of discharging. A timespan during the at least one of charging and of discharging the capacitor is measured, between a first predetermined charging level and a second different predetermined charging level of the addressed capacitor.
In an embodiment of the just addressed embodiment of the method, measuring of the timespan is performed by Time to Digital Conversion (TDC), e.g. as addressed in the U.S. Ser. No. 07/403,020 B2.
In a further embodiment of the method addressing applying a pressure sensing capacitor, one of the electrodes comprises a ceramic material membrane, preferably made of Al2O3.
In a further embodiment of the method according to the invention digital signal processing is applied.
The apparatus according to the present invention for measuring pressure, especially a vacuum pressure, in a compartment exposed to a pressure step, comprises:
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- measuring means for measuring an average pressure level in the compartment, averaged over a predetermined timespan and for generating a respective pressure level indicative signal;
- monitoring means for monitoring transient pressure step response oscillation frequency—fTSR—of the pressure in the compartment;
- evaluation means for evaluating the fTSR.
In an embodiment of the apparatus according to the invention, which may be combined with any embodiment of the apparatus still to be addressed, unless in contradiction, the measuring means and the monitoring means comprise a common capacitance pressure sensor with a capacitor, the capacity thereof being dependent from an input pressure to be sensed. They further comprise charging/discharging means for charging and discharging the capacitor, whereby at least one of charging and of discharging is performed through a resistive element, the resistivity thereof defining, together with the capacity of the addressed capacitor, the time course of the at least one of charging and of discharging. They further comprise a time measuring means for measuring a timespan, characteristic of the at least one of the charging and of the discharging through the resistive element.
Please note that the resistive element needs not be a discrete resistor, but may be realized e.g. by the resistivity of an electronic switch in conducting state or by a connecting wire etc.
In an embodiment of the just addressed embodiment of the apparatus, it comprises a clock unit which controls charging and discharging at a repetition frequency, which is at least 5 times, preferably at least 10 times higher than an expected fTSR, whereby the addressed repetition frequency, also called sampling frequency, is set to be preferably at least 0.5 kHz and even more preferred at least 5 kHz.
In a further embodiment of the apparatus the addressed time measuring means comprise a Time to Digital Converter (TDC).
In a further embodiment of the apparatus, which may be combined with any of the preaddressed embodiments and embodiments still to be addressed, unless in contradiction, the evaluation means comprise a digital signal processing unit, e.g. in the form of a ASIC.
In a further embodiment of the apparatus according to the invention, which may be combined with any of the preaddressed embodiments and embodiments still to be addressed, unless in contradiction, the measuring means and the monitoring means comprise a common pressure sensor, whereby at least the monitoring means comprise sampling means for sampling the output signal of the common pressure sensor at a sampling frequency which is at least 5 times, preferably at least 10 times higher than an expected fTSR. The sampling frequency is thereby preferably set to at least 0.5 kHz, and even more preferred to at least 5 kHz.
In an embodiment of the apparatus according to the invention, which may be combined with any of the preaddressed embodiments and embodiments still to be addressed, unless in contradiction, the measuring means and the monitoring means comprise a common capacitor pressure sensor with a capacitor, the capacity thereof being dependent from an input pressure, the capacitor comprising a membrane electrode of a ceramic material, preferably made of Al2O3 .
In a further embodiment of the apparatus according to the invention, which may be combined with any of the preaddressed embodiments and embodiments still to be addressed, unless in contradiction, the evaluation means comprise comparing means for comparing a signal representing the fTSR with a signal representing a reference fTSR.
In a further embodiment of the apparatus according to the invention, which may be combined with any of the preaddressed embodiments and embodiments still to be addressed, unless in contradiction, the evaluation means comprise a look-up table with a multitude of signals each representing a gas or gas mixture indicative reference fTSR and the comparing means are adapted for comparing a signal representing the fTSR as monitored with the multitude of signals representing the gas or gas mixture indicative reference fTSR. The comparing means are further adapted to output an output signal indicative for at least one specific gas or gas mixture, the signal representing the reference fTSR of the addressed at least one gas or gas mixture fitting best with the signal which represents the fTSR as monitored.
The invention shall now be further described and exemplified with the help of figures. The figures show:
Qualitatively, pressure courses as may be established and evaluated in a compartment by the present invention,
A signal dependent from the output signal S5 of pressure sensor 5 is input to a TSR analyzer unit 7 which outputs a signal S7 which is indicative for the fTSR. Additionally, the output signal S5 is exploited, as schematically shown by S′5 (PST) for measuring the stationary pressure in compartment 1, which may be the pressure prevailing in compartment 1 before the pressure step ps is applied, according to
This fTSR is further dependent from the parameter geometry of the inner space of compartment 1 as well as, to a relevant or to a neglectable extent, from the initial pressure level pi, at which the pressure step ps initiates, the pressure level at which the pressure step ps terminates as well as from the temperature prevailing in the gas or gas mixture within compartment 1. The output signal of TSR analyzer unit 7 is exploited as an indicative signal for the gas or gas mixture in compartment 1 at the moment pressure step ps is applied.
The fTSR is indicative for the gas or gas mixture in compartment 1, because it depends from sound velocity in compartment 1, which latter is dependent from gas species or gas mixture species.
Whereas the inventors of the present invention have up to now investigated on pressure step responses when applying a step with an initial pressure pi being a vacuum pressure and wherein the stationary step response pressure pST is ambient pressure or inversely, it is believed that the invention may be realized on any initial pressure level pi and any stationary step response level pST if the addressed slope of the applied pressure step ps is fast or steep enough.
Customarily the container 1 will be a compartment which is to be operated on a pressure level which is stationary. This to operate practical processes as e.g. vacuum process, e.g. vacuum coating or vacuum etching processes during respectively needed operation times. Thus, at least one of the initial pressure pi and of the stationary step response pressure level pST will have to be stationarily upheld during such processing. To do so customarily there is provided a pressure source, for vacuum pressure levels a vacuum pump, acting on compartment 1 as shown in
According to
The course qualitatively shown in
With an eye on
With an eye on the fact that the fTSR as monitored and identified by signal S7, is indicative for a gas or gas mixture or at least for a group of gases or gas mixtures, one may in an embodiment detect by the addressed processing a difference of gas or gas mixture prevailing on one hand in compartment 1 at one moment, and on the other hand at a different moment. Thereby, e.g. leakiness of the compartment 1 over long operating times may be detected. Such processing is addressed in
Applying a first and second and possibly even more pressure steps ps1, ps2 . . . may be performed in any combination of courses as exemplified in
According to
The gas or gas mixture in preload compartment 10 is normally the same gas or gas mixture as present in compartment 1. By abruptly opening valve 14 the pressure p10 and the pressure in compartment 1, p1, become equal, which results in a pressure step ps in compartment 1 with pressure sensor 5. One may have to consider the geometry of the combined system of preload compartment 10, lines 12, 12′, valve 14 and compartment 1 as co-determining the frequency fTSR. Thereby, it may be a good approach to in fact exploit such combined system as resulting compartment 1′, wherein further processing is performed. Clearly, the pressure p10 may be higher or lower than the pressure pi, at least one of these pressures may be a vacuum pressure.
In a most straight ahead embodiment of the method and apparatus according to the invention and as shown in
In a reference signal unit 22, in the simplest way, there is stored a reference signal which is indicative for the fTSR of that gas or gas mixture which is expected to be present in compartment 1. The reference signal indicative for the reference fTSR of a gas or gas mixture expected to be in compartment 1, has been provided and stored by analyzing the step response of that expected gas, in fact a reference gas, substantially following the process according to
Thus and according to
The following cases should be considered:
If the geometry of the inner space of compartment 1 and of reference compartment 1R are different, then at least one of the signals S7r and of S7 should be converted, so that fTSRR and fTSR to be in fact compared at comparator unit 20 refer to frequencies at equal geometries of the respective inner spaces.
If the initial pressure pi exploited for the pressure step in reference compartment 1R is different from the initial pressure pi as exploited in compartment 1 and the difference of such initial pressures is relevant, again at least one of S7R and S7 should be converted so that, at comparator unit 20, frequency comparison is performed with respect to frequencies established by step responses with equal initial pressures.
If the stationary step response pressure level as exploited in the reference compartment 1R is different from the stationary step response level pST as applied to compartment 1 and such difference is relevant with respect to fTSR, then again at least one of the output signals S7 and S7R should be converted so as to ensure that at comparator unit 20 as of
The same is valid if the pressure sensor 5 and the reference pressure sensor 5R are different and possibly even if analyzing in analyzer unit 7 and in reference analyzer unit 7R are different. Further, the same prevails if the gas temperature in reference compartment 1R is different from the gas temperature in compartment 1 when applying the respective pressure step ps and pSR.
A reference signal or more than one reference signals S7R, indicative for the respective fTSRR of specific gas or gas mixtures, may be provided from a remote instance, e.g. from a server via online communication or may be provided on a storing unit as on a chip to be exploited when practicing the invention.
As shown in
Thereby and in such a case the prevailing fTSR indicative signal S7 is compared in unit 20 with the reference frequency signals in the look-up table of unit 22. The comparator unit outputs a gas or gas species indicative signal GCOMP1 indicative for that gas or gas mixture G1, . . . Gn out of look-up table in unit 22, the reference fTSRR signal s7R fitting best with the fTSR-representing signal S7. Please note that similar fTSR may be indicative for a group of gases or gas mixtures rather than for specific gases or gas mixtures.
As shown schematically by the switches Q in
The following considerations prevail:
If it is intended to just monitor a difference of gas or gas mixtures prevailing in compartment 1 at the instances of applying ps1 and ps2, the output signal of comparator unit 20′ is just indicative of a gas or gas mixture difference ΔG, as none of the gases or gas mixtures prevailing in compartment 1 is known.
If, when the first pressure step ps1 is applied, the gas or gas mixture in compartment 1 is known, then the output signal of comparator unit 20′ is significant for approving or non-approving that the gas or gas mixture at the instance ps2 is applied, is or is not equal to the addressed known gas or gas mixture. In fact, if at the instance the first pressure step ps1 is applied to compartment 1, the gas or gas mixture contained therein is exactly known, then storing unit 30 becomes the reference signal unit 22 as of
According to
The capacitor 62 comprises, as an example, a rigid electrode 64 and, as a second electrode, a membrane 66. One side of membrane 66 is exposed to a reference pressure po within an interspace between the electrodes 64 and 66. The second surface of membrane 66 is exposed, as schematically shown in
As a function of pressure difference between pressure to be sensed and reference pressure po the membrane electrode 66 is deformed, e.g. bowing more or less out towards the lower of the addressed two pressures po and p1 and as schematically shown by the double arrow F in
After having charged the capacitor 62, the capacitor 62 is decharged via a resistive element R of accurately known resistivity value. According to
The output signal S74 and thereby specifically the time extent T of the output pulse is significant for the momentarily prevailing capacity value of capacitor 62. In a time measuring unit 76 a highly accurate measurement of the timespan T is performed and, based on the known characteristic of the capacitance pressure sensor, i.e. the known dependency of C(p) from pressure p, the pressure momentarily prevailing in compartment 1 is calculated in an analyzer unit 78. Charging/discharging capacitor 62 is controlled, as schematically shown by switch Q3, by means of a clock unit 80. Given a range of expected fTSR to be evaluated, charging and discharging of the capacitor 62 is performed at a repetition or sampling frequency fs, which is at least twice the highest fTSR expected. In a good embodiment the sampling frequency fs is at least 5 times, in an even better embodiment at least 10 times, higher than the addressed highest expected fTSR. The sampling frequency fs is to now selected to be at least 0.5 kHz and even better to be at least 5 kHz. Thus, by the addressed sensing technique the pressure course in compartment 1 is sampled at a respectively high sampling frequency. At the output of comparator unit 74 a pulse train is generated at the addressed charging and discharging sampling frequency fs, controlled by clock unit 80. The analyzer unit 78 in fact performs time to capacity to pressure to fTSR conversion and generates an output signal S78, which is evaluated in a comparator unit 20′ as was explained in context with.
Very accurate and highspeed measurement of the timespan T or more generically of a timespan significant for he discharging process of capacitor 62 through resistive element R is performed by constructing the time measuring unit 76 as a Time to Digital Converter (TDC). Especially in this case subsequent signal processing as by unit 78 and comparing unit 20′ is performed digitally, e.g. by Digital Signal Processing unit e.g. realized by an ASIC.
The signal output at output O86 accords with the sampled pressure course prevailing in compartment 1 and includes the transient step response with the respective oscillation at fTSR. It is this output signal which is further exploited, preferably by comparing with one or more than one reference fTSR signals as was explained in context with
In a compartment 1 filled with Helium a pressure step from 5 Torr to 750 Torr was applied by floating compartment 1. The resulting transient step response (a) including transient step response oscillation is shown in
Then, with the same compartment 1 at the same temperature the same experiment was done with argon. The course (b) is the result signal at O86, indicative for the resulting fTSR. The fTSR for Helium is about 0.3 kHz. The fTSR for Argon is about 0.1 kHz.
The sampling frequency fs is about 1.5 kHz.
As may be seen by evaluating the respective transient step response oscillation frequencies fTSR, which are specific for a gas or gas mixture prevailing in compartment 1, either the gas or gas mixture prevailing in that compartment or a change of gas or gas mixture occurring in that compartment may be monitored. According to the present invention the same pressure sensor is exploited on one hand to monitor the average or stationary pressure level in compartment 1 as is exploited for practical processing in compartment 1 as well as the transient pressure step response indicative for a gas or gas mixture prevailing in compartment 1 when a pressure step is applied.
With an eye on the charge/discharge sampling as exemplified in context with
In
Claims
1) A method of measuring pressure, especially vacuum pressure of a gas or gas mixture in a compartment of predetermined geometry of inner space, comprising measuring said pressure by a pressure sensor, applying to said compartment at least one step of pressure and monitoring by said sensor the transient step response oscillation frequency of the pressure in said compartment as indicative of the gas or gas mixture in said compartment, said measuring lasting longer than said transient step response.
2) The method of claim 1, wherein said applying of said at least one step of pressure comprises applying a pressure step from ambient pressure to a target pressure preferably to a target vacuum pressure.
3) The method of claim 1, wherein said applying of said at least one step of pressure comprises applying a pressure step from a pressure in said compartment, preferably a vacuum pressure, to ambient pressure.
4) The method of claim 1, comprising applying said pressure step by abruptly expanding a gas from said compartment or into said compartment.
5) The method of claim 1, monitoring said frequency in time domain or in frequency domain.
6) The method of claim 1, comprising providing at least one reference transient step response oscillation frequency—fTSR—signal indicative for a fTRS of at least one gas or gas mixture and comparing a signal dependent from said fTSR monitored with a said reference fTRS signal.
7) The method of claim 6, comprising providing a multitude of gas or gas mixture specific reference fTSR signals preferably in form of a look-up table and comparing said signal dependent from said fTRS as monitored by said pressure sensor with said reference fTSR signals thereby outputting a gas or gas mixture indicative signal for that specific gas or gas mixture, the reference fTSR signal thereof fitting best with said signal dependent from said fTSR as monitored.
8) The method of claim 1, comprising providing said at least one reference fTSR signal by providing a reference compartment of predetermined geometry of inner space, applying to said reference compartment at least one reference step of pressure, monitoring by a further pressure sensor the resulting fTSR and storing a signal dependent from said resulting fTSR in said reference compartment as said reference fTSR signal.
9) The method of claim 8, wherein said dependent signal stored is derived from said fTSR as a function of at least one of
- a difference of predetermined geometry of said compartment and of said reference compartment, if existing and not neglectable,
- a difference of pressure level at which said fTSR in said reference compartment and in said compartment are monitored, if existing and relevant,
- a difference of temperatures at which said fTSR in said reference compartment and in said compartment are monitored, if existing and not neglectable.
10) The method of claim 8, comprising deriving said signal dependent from said fTSR monitored as a function of at least one of
- a difference of predetermined geometry of said compartment and of said reference compartment, if existing and not neglectable,
- a difference of pressure level at which said fTSR in said reference compartment and in said compartment are monitored, if existing and not neglectable,
- a difference of temperatures at which said fTSR in said reference compartment and in said compartment are monitored, if existing and not neglectable.
11) The method of claim 9, wherein there is valid: said geometry of said reference compartment is equal to the said geometry of said compartment or said reference compartment is said compartment.
12) The method of claim 8, wherein there is valid: said further pressure sensor is equal to said pressure sensor or said further pressure sensor is said pressure sensor.
13) The method of claim 8, wherein there is valid at least one of:
- said step of said reference pressure is equal to said step of pressure,
- the pressure level in said reference compartment before said reference step is applied is equal to the pressure level in said compartment before said step is applied,
- the stationary pressure level in said reference compartment before said reference step is applied is equal to the stationary pressure level in said compartment before said step is applied,
- the stationary pressure level in said reference compartment after said reference step is applied is equal to the stationer pressure level in said compartment after said step is applied,
- the temperature in said reference compartment during applying said reference step is equal to the temperature in said compartment during said step being applied.
14) The method of claim 1, wherein at least said monitoring by said sensor comprises sampling a signal dependent from an output signal of said sensor at a sampling frequency which is at least 5 times, preferably at least 10 times higher than said fTSR, said sampling frequency being at least 0.5 kHz, even more preferred at least 5 kHz.
15) The method of claim 1, wherein said measuring and said monitoring by said pressure sensor comprises:
- providing a pressure sensing capacitor with two electrodes, the capacity of said capacitor being dependent from said pressure in said compartment,
- electrically monitoring the course of said capacity of said capacitor.
16) The method of claim 15, thereby monitoring said course of said capacity by sampling, each sampling comprising:
- charging and discharging said capacitor, thereby performing at least one of said charging and of said discharging of said capacitor via a resistive element of predetermined resistivity, which, together with said capacity being decisive for the time course of said at least one of charging and of discharging, and measuring a time span during said at least one of charging and of discharging said capacitor between a first predetermined charging level and a second different predetermined charging level.
17) The method of claim 16, said measuring of said time span being performed by Time to Digital Conversion (TDC).
18) The method of claim 15, wherein one of said electrodes comprises a ceramic material membrane, preferably made of Al2O3.
19) The method of claim 1, comprising digital signal processing.
20) An apparatus for measuring pressure, especially vacuum pressure, in a compartment exposed to a pressure step, comprising:
- measuring means for measuring an averaged pressure level in said compartment, averaged over a predetermined time span, and for generating a respective pressure level indicative signal;
- monitoring means for monitoring transient pressure step response oscillation frequency of the pressure in said compartment—fTSR—;
- evaluation means for evaluating said fTSR.
21) The apparatus of claim 20, said measuring means and said monitoring means comprising a common capacitance pressure sensor, with a capacitor, the capacity thereof being dependent from an input pressure to be sensed and charging/discharging means for charging and discharging said capacitor, thereby at least one of charging and of discharging being performed through a resistive element, the resistivity value thereof defining together with the capacity value of said capacitor, the course of said at least one of charging and of discharging, and time measuring means for measuring a time span, characteristic of said at least one of said charging and of said discharging through said resistive element.
22) The apparatus of claim 21, comprising a clock unit, controlling said charging and discharging at a repetition frequency which is at least 5 times, preferably at least 10 times higher than an expected fTSR, said repetition also called sampling frequency being preferably at least 0.5 kHz, more preferred at least 5 kHz.
23) The apparatus of claim 21, said time measuring means comprising a Time to Digital Converter.
24) The apparatus of claim 20 said evaluation means comprising a digital signal processing unit.
25) The apparatus of claim 20, said measuring means and said monitoring means comprising a common pressure sensor and at least said monitoring means comprising sampling means for sampling the output signal of said common pressure sensor at a sampling frequency which is at least 5 times, preferably at least 10 times higher than an expected fTSR, said sampling frequency is preferably at least 0.5 kHz, even more preferred at least 5 kHz.
26) The apparatus of claim 21, wherein said measuring means and said monitoring means comprise a common capacitor pressure sensor with a capacitor, the capacity thereof being dependent from an input pressure, said capacitor comprising a membrane electrode of a ceramic material, preferably made of Al2O3.
27) The apparatus of claim 21, wherein said evaluation means comprises comparing means for comparing a signal representing said fTSR with a signal representing a reference fTSR.
28) The apparatus of claim 20, wherein said evaluation means comprises a look up table with a multitude of signals representing gas or gas mixture indicative reference fTSR and said comparing means being adapted for comparing a signal representing said fTSR with said multitude of signals representing said indicative reference fTSR and further being adapted to output an output signal indicative of at least one specific gas or gas mixture, the signal representing said reference fTSR of said at least one specific gas or gas mixture fitting best with said signal representing said fTSR.
Type: Application
Filed: Sep 9, 2013
Publication Date: Aug 4, 2016
Patent Grant number: 10107703
Inventors: Christian BERG (Stafa), Martin WÜEST (Malans)
Application Number: 14/917,886